Wind tunnel test of airfoil with erosion and leading edge protection

Abstract

This paper describes wind tunnel tests of a NACA 633 − 418 airfoil with erosion and leading edge protection. Measurements are carried out at high Reynolds number (Re = 5 million) representing modern wind turbines. Three examples of deviations from the perfect airfoil surface are shown. It is seen how the presence of a roughness mesh degrades the aerodynamics and that the presence of the mesh is more important than the actual topology of the mesh. That is also the case for the stall strips where a small strip influences the performance slightly less than a big stall strip, but the presence of the stall strip alone is influencing the performance significantly. Finally, a simulated leading edge protection (LEP), represented by a sheet of paper, can influence the performance significantly as the paper leads to a backward facing step. Furthermore, the measurements showed that correct mounting of LEP is important to avoid too big losses in aerodynamic performance. Investigating the impact of reduced airfoil performance for the rotor performance showed losses in annual energy production of between 0.3% and 4.0%. All in all the wind tunnel tests reflected that leading edge damages have a significant impact on the aerodynamic performance.